The present invention relates to a multi-layer superconducting circuit substrate, particularly to a multi-layer superconducting circuit substrate suitable for use in a high speed computer such as a supercomputer, and a process for manufacturing same. A substrate used for high speed processing requires a conductive material having a low electrical resistance, in addition to an insulating material having a low dielectric constant, to ensure an efficient transmission of signals.
As a substrate for high speed processing, a multi-layer ceramic substrate is known in which a glass-ceramic material, i.e., a complex of a ceramic and a glass (dielectric constant .epsilon..apprxeq.5), is used as an insulating material and copper (resistivity .rho.=1.7 .OMEGA..cm) is used as a conducting material (for example, see Yogyo Kyokai Annual Conference Digest, 1985, P. 533).
Japanese Unexamined Patent Publication (Kokai) No. 60-173885, published on Nov. 7, 1985, describes a superconductive oxide material of BaBiO.sub.3-.delta. (0.ltoreq..delta.&lt;0.5) wherein less than 50% by atom of Ba is replaced by Sr, Pb, Sc, Y or a Lanthanide element, the superconductive oxide material having a superconducting transition temperature of about 12 K.; and a process for manufacturing a superconductive oxide material of BaBiO.sub.3-.delta. (0.ltoreq..delta.&lt;0.5); the process including the steps of uniformly mixing a Ba compound and a Bi compound, calcining the mixture in an oxidizing atmosphere at a temperature of more than 600.degree. C., pulverizing the calcined product, pressing the resultant powder to form a body, and annealing the body in an atmosphere containing more than 10 kg/cm.sup.2 of oxygen at 700.degree. C. to compensate for a large amount of oxygen lost in the calcining step.
Also known are the following oxide superconductive materials:
(1) La-Ba-Cu-O system:
Bednorz: Z. Phys. B. 64, 189, 1986; PA1 Uchida: J. J. A. P. vol. 26, No. 1, L1, 1987; PA1 Chu: Physical Review Letters; vol. 58, No. 4, 405, 1987; PA1 Jorgensen: Physical Review Letters; vol. 58, No. 10, 1024, 1987; PA1 Cava: Physical Review Letters: vol. 58, No. 4, 408, 1987; PA1 Mattheiss: Physical Review Letters; vol. 58, No. 10, 1028, 1987; and PA1 Hor: Physical Review Letters; vol 58, No. 9, 911, 1987; and PA1 Wu: Physical Review Letters; vol. 58, No. 9, 908, 1987.
(2) La-Sr-Cu-O system:
(3) Y-Ba-Cu-O system:
Specifically:
(1) the La-Ba-Cu-O system includes
______________________________________ La.sub.4 BaCu.sub.5 O.sub.5(3-y) T.sub.cf 13K, T.sub.co 35K; La.sub.4.25 Ba.sub.0.75 Cu.sub.5 O.sub.5(3-y) La.sub.0.8 Ba.sub.0.2 CuO.sub.(3-y) T.sub.cf 4K; La.sub.0.85 Ba.sub.0.15 CuO.sub.(3-y) (La.sub.0.8 Ba.sub.0.2).sub.2 CuO.sub.(4-y) T.sub.cf 20K, T.sub.co 36K; (La.sub.0.85 Ba.sub.0.15).sub.2 CuO.sub.(4-y) La.sub.1.85 Ba.sub.0.15 CuO.sub.4 T.sub.cf 20K, T.sub.co 35K; La.sub.1.90 Ba.sub.0.10 CuO.sub.4 ______________________________________
(2) the La-Sr-Cu-O system includes
______________________________________ La.sub.1.9 Sr.sub.0.1 CuO.sub.4 La.sub.1.8 Sr.sub.0.2 CuO.sub.4: T.sub.cf 28.5K, T.sub.cm 33.1K, T.sub.co 36.5K; La.sub.1.7 Sr.sub.0.3 CuO.sub.4: T.sub.cm 15K, T.sub.co 35K; La.sub.1.925 Sr.sub.0.075 CuO.sub.4: T.sub.cf 26.5K, T.sub.cm 34K, T.sub.co 52K, La.sub.1.85 Sr.sub.0.15 CuO.sub.4: T.sub.cf 36K, t.sub.cm 37.5K, T.sub.co 40K; ______________________________________
(3) the Y-Ba-Cu-O system includes
______________________________________ (Y.sub.0.6 Ba.sub.0.4).sub.2 CuO.sub.4-.delta.: T.sub.cf 88.5K, &gt;77K, T.sub.co .gtoreq. 100K; Y-Ba-Cu-O T.sub.c 77K, T.sub.co 100K; (by Keiichi Ogawa) Y-Ba-Cu-O: T.sub.c 95K; (by Molecular Institute and Tohoku University) Y.sub.0.4 Ba.sub.0.6 CuO.sub.3: T.sub.c 93, T.sub.co 123K. (by Kazumasa Togano) ______________________________________
At present, the conducting materials used in substrates have an electrical resistance which inhibits the design of even longer or finer interconnection patterns. A demand therefore exists for a substrate for high speed processing, the substrate using a conductivity material having an even lower electrical resistance, which substrate is to be used in a future generation computer. Although a superconductive oxide material meets this requirement, i.e., a lower electrical resistance, it is difficult to form a superconductive oxide material into an interconnection pattern. New interconnection patterns should have definite peripheries which are at least as definite as those of the copper patterns, in order to reduce interactions between neighboring patterns, since the density of the patterns will be made higher.